1. Field of the Invention
The present invention relates to a computer system and a frame transmitting method which is adopted thereto.
2. Description of the Related Art
Some computer systems are equipped with a pair of a central processing unit and an input/output unit which are connected via two data transmitting routes. This kind of the computer systems are disclosed in, for example, Unexamined Japanese Patent Application KOKAI Publication No. H11-119802 and Japanese Patent No. 3169861. The disclosures of the above-indicated documents are incorporated herein by reference.
In general, this kind of the computer systems use one of the data transmitting route for transmitting frames included in data, and the other data transmitting route as a “back-up”. In a case where a failure occurs on one of the data transmitting route while transmitting frames, the computer systems continues transmitting frames using the back-up (the other of the data transmitting route). That is, the computer systems switch the data transmitting routes when a fault occurs.
The computer system disclosed in Unexamined Japanese Patent Application KOKAI Publication No. H11-119802 switches two of data transmitting routes in accordance with a control of an OS (Operating System), a software, etc. In this computer system, if the data transmitting routes are switched while instructions which are not necessary responses are transmitted to the input/output unit, the OS can not specify which instructions have been sent to the input/output unit among all in some case. In this case, the OS may not be able to specify which instructions are to be re-transmitted, and this results in “system-down”. Therefore, there is some room for improvement in reliability.
The computer system disclosed in Japanese Patent No. 3169861 once suspends transmitting frames when switching two of data transmitting routes. Transmitting frames is held until the switching is completed. Thus, transmitting frames is not carried out continuously, and there is some room for improving efficiency of frame transmission.